A climate control system 10 in a vehicle regulates temperature and humidity in the vehicle as shown in FIG. 1. The climate control system 10 includes a compressor 12, a condenser 14, an expansion element 16, an evaporator 18, and a heater core 20. The compressor 12 moves a refrigerant through the refrigeration circuit of the climate control system 10, which includes the compressor 12, the condenser 14, the expansion element 16, and the evaporator 18. The compressor 12, which may be a cycling compressor or a variable displacement compressor, compresses and circulates the refrigerant vapor through the condenser 14. The condenser 14 condenses the refrigerant vapor into a liquid and rejects heat, thereby cooling the liquid. The condenser 14 passes the liquid through the expansion element 16, such as an expansion valve, into the evaporator 18. The cooled refrigerant liquid passes through the evaporator 18 and returns to the compressor 12 as vapor.
A blower or fan 22 forces air 24 through the evaporator 18 and the heater core 20 into a passenger compartment 26. As the refrigerant liquid inside the evaporator 18 cools the air 24, the liquid absorbs heat from the air 24 and returns to vapor. The evaporator 18 cools the air 24 to a minimum temperature. Typically, the evaporator 18 is configured to cool the air 24 to a temperature just above freezing, effectively removing all humidity from the air 24. A portion of the air 24 then passes through the heater core 20. The heater core 20 is connected to the vehicle's coolant system 28, which circulates water solution through the heater core 20. For example, the water solution may include 50% water and 50% glycol. In this manner, the heater core 20 heats a portion of the air 24 according to a desired temperature, which is further determined from passenger feedback or thermostat controls. The heated air is recirculated with the cooled air to achieve the desired temperature and circulated into the passenger compartment 26. Additionally, the climate control system 10 may include a controller (not shown) that communicates with components such as the compressor 12, the evaporator 18, and the blower 22.
As described, the climate control system 10 operates to cool the air 24 to a low band temperature, such as a minimum temperature, regardless of the desired temperature, and then subsequently reheats the air. For example, the low band may be slightly above freezing, or 38° F. Alternatively, the climate control system 10 may adjust the low band according to other factors, such as the speed of the blower 22, a mode setting, and the desired temperature. For example, the mode setting can be used to select panel, bi-level, floor, mixed, and defrost modes as are known in the art. Therefore, elements of the climate control system 10, such as the compressor 12, operate more than necessary and increase fuel consumption. In certain circumstances, maximum climate control usage may account for as much as a 4 mile per gallon increase of fuel consumption.